Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 b2655c23ec984ff0…

MALICIOUS

Office (OLE) / .XLSX

186.6 KB First seen: 2022-03-01
MD5: 313487ea2961de7d5b451ff47cb70373 SHA-1: 52bb294a2b82ca3d932ab399edc9246c28d5988d SHA-256: b2655c23ec984ff04ac2229b96ef9faaa1d89f79fd028fdca5ea8fd3be76922c
280 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1566.001 Spearphishing Attachment

The file is a password-encrypted Office document identified by ClamAV as Doc.Downloader.Formbook. High-severity heuristics indicate it contains an Equation Editor OLE object, specifically triggering CVE-2018-0798. This suggests the document is designed to exploit this vulnerability to execute a downloader payload, likely leading to the installation of Formbook malware. No scripts were extracted, but the combination of encryption, exploit carrier, and Equation Editor OLE object strongly points to this attack vector.

Heuristics 7

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Default-encrypted OOXML embedded OLE object xl/embeddings/oleObject1.bin contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Default-encrypted OOXML contains embedded Equation Editor data with anomalous native stream bytes consistent with a CVE-2018-0798-style exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like.
  • Encrypted Office package with CFB FAT corruption critical OLE_ENCRYPTED_AND_MALFORMED
    Encrypted-package shape co-occurs with FAT-chain corruption — the documented combined evasion form.
  • ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
  • Default-encrypted OOXML exploit carrier layout high OOXML_ENCRYPTED_EXPLOIT_CARRIER_SHAPE
    Default-password encrypted OOXML package contains embedded OLE object parts and additional activation/decoy parts. This layout is common in malicious Excel exploit delivery and requires inspecting the decrypted package.
  • Office document is password-encrypted medium OFFICE_ENCRYPTED_PACKAGE
    OLE container holds MS-OFFCRYPTO encrypted package (Standard Encryption (Office 2007, AES)).
  • Office OOXML encrypted with default VelvetSweatshop password medium OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML
    OLE EncryptedPackage decrypts with Excel's built-in VelvetSweatshop password. Office opens this transparently, and malware uses it to hide OOXML exploit parts from scanners that only inspect the outer OLE container.